Changes in equity and comprehensive income line items.

No definition available.

Name:	mfin_ChangesInEquityAndComprehensiveIncomeLineItemsLineItems
Namespace Prefix:	mfin_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Increase in preferred stock dividend rate percentage.

+ References

No definition available.

+ Details

Name:	mfin_IncreaseInPreferredStockDividendRatePercentage
Namespace Prefix:	mfin_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow to reacquire preferred stock during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsForRepurchaseOfPreferredStockAndPreferenceStock
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The percentage rate used to calculate dividend payments on preferred stock.

+ References

No definition available.

+ Details

Name:	us-gaap_PreferredStockDividendRatePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_PreferredStockSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Proceeds from issuance of capital stock which provides for a specific dividend that is paid to the shareholders before any dividends to common stockholders and which takes precedence over common stockholders in the event of liquidation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis=mfin_CapitalPurchaseProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=mfin_SeriesABCAndDNoncumulativePerpetualPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=mfin_SeriesESeniorNoncumulativePerpetualPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Small Business Lending Fund Program (SBLF) and Troubled Assets Relief Program (TARP) - Additional Information (Detail) - Capital Purchase Program [Member] - USD ($)				3 Months Ended	6 Months Ended
	Apr. 02, 2018	Jul. 21, 2011	Feb. 27, 2009	Mar. 31, 2016	Jun. 30, 2018
US Treasury Securities [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Aggregate purchase price	$ 26,303,000
US Treasury shares purchased		26,303
Series ABC and D Non-cumulative Perpetual Preferred Stock [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Aggregate purchase price			$ 21,498,000
Redemption of preferred stock					$ 4,000,000
Series E Senior Non-Cumulative Perpetual Preferred Stock [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Aggregate purchase price		$ 26,303,000
Percentage of dividend payment rate					1.00%
Percentage of dividend payment rate increased				9.00%